3GPP (3rd Generation Partnership Project) is a project which performs investigation and creation of specification of a mobile communication system on the basis of a network in which W-CDMA (Wideband-Code Division Multiple Access) and GSM (Global System for Mobile Communications) are developed. In 3GPP, the W-CDMA system has been standardized as the 3rd generation cellular mobile communication system, and the services have been launched one after another. In addition, HSDPA (High-speed Downlink Packet Access) with a transmission speed further increased also has been standardized, and the services have been launched. In 3GPP, investigation with respect to a mobile communication system which realizes a furthermore high-speed data transmission and reception (hereinafter, referred to as “LTE-A (Long Term Evolution-Advanced)” or “Advanced-EUTRA”) using evolution of the 3rd generation radio access technology (hereinafter, referred to as “LTE (Long Term Evolution)” or “EUTRA (Evolved Universal Terrestrial Radio Access)”) and a wider frequency band, has been promoted.
As a communication system in LTE, an OFDMA (Orthogonal Frequency Division Multiple Access) method where user-multiplexing is performed by using mutually orthogonal subcarriers and an SC-FDMA (Single Carrier-Frequency Division Multiple Access) method are investigated. That is, in a downlink, the OFDMA method that is a multi-carrier communication system, and in an uplink, the SC-FDMA method that is a single-carrier communication system, are proposed.
On the other hand, as a communication system in LTE-A, introduction of the OFDMA method in a downlink, and a Clustered-SC-FDMA (Clustered-Single Carrier-Frequency Division Multiple Access, also referred to as DFT-S-OFDM with Spectrum Division Control, or DFT-precoded OFDM) method in addition to the SC-FDMA method in an uplink is investigated. Here, in LTE and LTE-A, the SC-FDMA method and Clustered-SC-FDMA method proposed as an uplink communication system, in terms of characteristics of the single-carrier communication method (owing to single-carrier characteristics), has a feature that PAPR (Peak to Average Power Ratio: transmit power) at the time of transmitting data (information) can be suppressed to a low level.
In addition, in LTE-A, it is investigated that while a frequency band used in a general mobile communication system is contiguous, a plurality of contiguous and/or non-contiguous frequency bands (hereinafter, referred to as “component carrier, element carrier (CC: Component Carrier)”, or “carrier component, carrier element (CC: Carrier Component)”) are used complexly and operated as one frequency band (wider frequency band) (frequency band aggregation: also referred to as Carrier aggregation, Frequency aggregation or the like). In addition, it is also proposed that for a base station apparatus and a mobile station apparatus to perform communication more flexibly using a wider frequency band, a frequency band used for downlink communication and a frequency band used for uplink communication are made to have a different frequency bandwidth (Asymmetric carrier aggregation) (Non-patent Document 1).
FIG. 6 is a figure describing a carrier-aggregated mobile communication system in a conventional technology. It is also referred to as symmetric frequency band aggregation (Symmetric carrier aggregation) that a frequency band used for communication of a downlink (DL) and a frequency band used for communication of an uplink (UL) are made to have the same bandwidth as shown in FIG. 6. As shown in FIG. 6, the base station apparatus and the mobile station apparatus can perform communication in a wider frequency band composed of a plurality of component carriers by using complexly a plurality of component carriers that is contiguous and/or non-contiguous frequency bands.
In FIG. 6, as an example, it is shown that a frequency band used for downlink communication having a bandwidth of 100 MHz (hereinafter, also referred to as DL system band, DL system bandwidth) is composed of five downlink component carriers (DCC1, DCC2, DCC3, DCC4, and DCC5) each having a bandwidth of 20 MHz. In addition, as an example, it is shown that a frequency band used for uplink communication having a bandwidth of 100 MHz (hereinafter, also referred to as UL system band, UL system bandwidth) is composed of five uplink component carriers (UCC1, UCC2, UCC3, UCC4, and UCC5) each having a bandwidth of 20 MHz.
In FIG. 6, downlink channels such as a physical downlink control channel (hereinafter, PDCCH), and a physical downlink shared channel (hereinafter, PDSCH) are mapped on each downlink component carrier. The base station apparatus allocates using PDCCH, to the mobile station apparatus, control information (resource allocation information, MCS (Modulation and Coding Scheme) information, HARQ (Hybrid Automatic Repeat Request) processing information, or the like) for transmitting a downlink transport block transmitted using PDSCH, and transmits the downlink transport block to the mobile station apparatus using PDSCH. Here, in FIG. 6, the base station apparatus can transmit up to five downlink transport blocks (PDSCH may be used) to the mobile station apparatus in the same subframe.
In addition, uplink channels such as a physical uplink control channel (hereinafter, PUCCH), and a physical uplink shared channel (hereinafter, PUSCH) are mapped on each uplink component carrier. The mobile station apparatus transmits using PUCCH and/or PUSCH, to the base station apparatus, channel state information (CSI: Channel Statement Information or Channel Statistical Information), and/or information (may be information indicating ACK/NACK for PDSCH) indicating ACK/NACK (positive response: Positive Acknowledgement/negative response: Negative Acknowledgement, ACK or NACK signal) of HARQ for a downlink transport block, and/or uplink control information (UCI) such as a scheduling request (SR). Here, in FIG. 6, the mobile station apparatus can transmit up to five uplink transport blocks (PUSCH may be used) to the base station apparatus in the same subframe.
Here, the channel state information (CSI) transmitted (reported, fed back) to the base station apparatus from the mobile station apparatus indicates the information (information indicating a channel quality for downlink) indicating a channel quality for a downlink signal transmitted from the base station apparatus. The mobile station apparatus measures (calculates, generates) a channel quality for a downlink signal transmitted from the base station apparatus, and transmits (reports, feeds back) it to the base station apparatus as the channel state information.
In the information, which is transmitted to the base station apparatus from the mobile station apparatus, indicating the channel state for the downlink signal, included are channel state information (CSI), and/or a channel quality identifier (CQI), and/or a precoding matrix indicator (PMI), and/or a rank indicator (RI).
Here, PMI and/or RI are used when the base station apparatus and the mobile station apparatus perform communication based on transmission diversity systems such as SDM (Space Division Multiplexing: space-multiplexing technology) and SFBC (Space-Frequency Block Diversity) using MIMO (Multiple Input Multiple Output), and CDD (Cycle Delay Diversity). MIMO is a generic name for a multi-input/multi-output system or technology, and the base station apparatus and the mobile station apparatus perform transmission with a plurality of input/output branches for the signal using a plurality of antennas in a transmitting side and a receiving side.
Here, a unit of a signal sequence which can be space-multiplexed and transmitted using MIMO is referred to as a stream, and the number (Rank) of the streams is determined by the base station apparatus in consideration of a channel state. In this case, the number of streams requested by the mobile station apparatus is transmitted to the base station apparatus as RI from the mobile station apparatus.
Furthermore, at the time of using SDM in a downlink, a preprocessing (hereinafter, referred to as “precoding”) is performed on the transmission signal sequence in advance in order to separate correctly information on a plurality of streams transmitted from each antenna. Information on this precoding can be measured (calculated, generated) by the mobile station apparatus on the basis of an estimated channel state, and is transmitted as PMI from the mobile station apparatus to the base station apparatus.
Similarly, FIG. 7 is a figure describing an asymmetric carrier-aggregated mobile communication system in a conventional technology. As shown in FIG. 7, the base station apparatus and the mobile station apparatus configure a frequency band used for downlink communication and a frequency band used for uplink communication to have a different bandwidth, and can perform communication in a wider frequency band using complexly component carriers that are contiguous and/or non-contiguous frequency bands constituting these frequency bands.
In FIG. 7, as an example, it is shown that a frequency band used for downlink communication having a bandwidth of 100 MHz is composed of five downlink component carriers (DCC1, DCC2, DCC3, DCC4, and DCC5) each having a bandwidth of 20 MHz, and a frequency band used for uplink communication having a bandwidth of 40 MHz is composed of two uplink component carriers (UCC1 and DCC2) each having a bandwidth of 20 MHz.
Here, in FIG. 7, downlink/uplink channels are mapped on downlink/uplink component carriers, respectively, and the base station apparatus allocates PDSCH to the mobile station apparatus using PDCCH and transmits a downlink transport block to the mobile station apparatus using PDSCH. That is, in FIG. 7, the base station apparatus can transmit up to five downlink transport blocks (PDSCH may be used) to the mobile station apparatus in the same subframe.
In addition, the mobile station apparatus, using PUCCH and/or PUSCH, transmits to the base station apparatus channel state information, and/or information indicating ACK/NACK in HARQ for a downlink transport block (may be information indicating ACK/NACK for PDSCH), and/or uplink control information such as a scheduling request. Here, in FIG. 7, the mobile station apparatus can transmit up to two uplink transport blocks (PUSCH may be used) to the base station apparatus in the same subframe.
FIG. 8 is a figure showing an example of transmission of channel state information from the mobile station apparatus to the base station apparatus in a conventional technology. A base station apparatus 801 transmits to the mobile station apparatus a downlink signal 803 indicating by using which radio resource (radio resource block) a mobile station apparatus 802 transmits an uplink signal 804 including channel state information. The mobile station apparatus transmits channel state information to the base station apparatus using the radio resource indicated by the base station apparatus.
In FIG. 8, for example, the mobile station apparatus maps periodic channel state information (P-CSI) on the PUCCH resource allocated by the base station apparatus and transmits it to the base station apparatus. In addition, for example, the mobile station apparatus maps aperiodic channel state information (A-CSI) on the PUSCH resource allocated by the base station apparatus and transmits it to the base station apparatus.
For example, the base station apparatus transmits a transmission request of channel state information on PDCCH allocating the PUSCH resource to the mobile station apparatus (for example, sets a CSI request transmitted on PDCCH to “1”), and the mobile station apparatus having received this information maps channel state information on the PUSCH resource allocated by the base station apparatus and transmits it to the base station apparatus (Non-patent Document 2).